Robotic legs move just like yours

Emma Woollacott, 7th July 2012

US researchers have built what they say is the first set of robotic legs that walk just like a human being.

They've based their design on the neural architecture, musculoskeletal architecture and sensory feedback pathways in humans, making the legs more biologically accurate than ever before.

Not only are they a natural for robot storm-troopers, they could improve efforts to help spinal cord injury patients recover the ability to walk. And we can't help thinking they'd be perfect for exercising Boston Dynamics' Alphadog, too.

A key component of the human walking system is the central pattern generator (CPG) - a neural network in the lumbar region of the spinal cord that generates rhythmic muscle signals, allowing people to walk without needing to think about it.

The simplest form of a CPG is a half-centre, which consists of just two neurons that take turns to fire signals, and it's this that the team's decided to mimic.

Information's delivered back to the half-centre by various sensors, including a set that sense force in the limb when the leg's pressed against the ground.

"Interestingly, we were able to produce a walking gait, without balance, which mimicked human walking with only a simple half-centre controlling the hips and a set of reflex responses controlling the lower limb," says Dr Theresa Klein of the University of Arizona.

She says she suspects that babies start off with a simple half-centre, like the one used in this robot, but learn a network for a more complex walking pattern over time.

This could explain why tiny babies cycle their legs when placed on a treadmill – a simple half-centre is already in place.

"This underlying network may also form the core of the CPG and may explain how people with spinal cord injuries can regain walking ability if properly stimulated in the months after the injury," says Klein.